Method for purifying and digesting radioactive insects in marine water body or sediment

Abstract

The invention belongs to the field of marine research, and particularly relates to a method for purifying and digesting radioactive insects in a marine water body or sediment. The invention provides a method for purifying radioactive insects in a water body or sediment, which comprises the following steps: mixing the radioactive insects with hydrogen peroxide, performing ultrasonic oscillation, separating and cleaning, and effectively removing organic matters or authigenic aluminosilicate rocks. The invention also provides a method for digesting the purified radioactive insects, which comprises the following steps: reacting the purified radioactive insects with sodium hydroxide in a high-temperature reaction kettle or under a water bath condition, and neutralizing, so that the sample loss is low.

Description

Technical Field

[0001] The invention belongs to the field of ocean research, and in particular relates to a method for purifying and digesting radiolarians in ocean water or sediments. Background Art

[0002] Radiolaria are a group of marine protozoa widely distributed throughout the world's oceans. They are categorized into the groups of actinopterygids, polycystic worms, foraminifera, and lanceolate worms. They are more abundant in tropical waters and the open ocean, but less abundant in coastal waters. Different species of radiolaria are selective for marine environments such as temperature, salinity, and depth. Therefore, the abundance and distribution of radiolarians in the ocean are used to study the evolution of marine environments. Furthermore, compared to marine calcareous organisms (such as foraminifera, CaCO₃), radiolarians are more easily preserved in sediments due to their relatively insoluble siliceous skeleton structure (amorphous silicon, SiO₂·nH₂O), making them important tools for studying paleoclimate and paleoceanography.

[0003] Radiolarians are primarily composed of organic matter and amorphous silica skeletons. As their life cycle ends, they gradually sink to the seafloor and are preserved in sediments. During the sedimentation process, some of the radiolarian organic matter decomposes and mineralizes, leaving only a small portion preserved. Authigenic aluminosilicates in the sediments adhere to the radiolarian surfaces, inhibiting further dissolution and mineralization of the radiolarian skeletons and promoting their long-term burial and preservation in the sediments. Research on radiolarians primarily focuses on their species, morphology, abundance, elemental content and ratios, and silicon isotope analysis. During this research process, the organic matter and authigenic aluminosilicates on the surface of the radiolarian silica skeletons in water and sediments must be removed to allow the purified radiolarians to be used for subsequent morphological and chemical analysis. During the research process, it was discovered that the removal efficiency of radiolarian organic matter in water and sediments is low. Traditional weak acid treatment methods (such as dilute hydrochloric acid) are difficult to completely remove the authigenic aluminosilicate rocks (containing elements such as silicon, aluminum, germanium, and iron) attached to the surface of radiolarians in sediments. The heating process changes the physical structure of the radiolarian shells (for example, the amorphous silicon structure loses some crystalline water, resulting in changes in physical properties), ultimately affecting the accurate analysis of the radiolarian physical and chemical composition (such as the ratios of elements such as silicon and aluminum, and silicon and germanium). In addition, during the analysis of radiolarian chemical composition and silicon isotopes, the purified solid radiolarian skeletons need to be digested into dissolved silicon. The traditional hot alkaline solution digestion process is slow, affecting the efficiency of research work, and the use of hydrofluoric acid greatly increases the safety risks of the experimental process and poses a serious threat to environmental pollution. Existing research programs (CN202311552883.2, CN202311552970.8, CN202320586200.4, CN201810802300.X) mainly focus on the detection and morphological analysis of radiolarians or the research on radiolarian pretreatment methods in rocks. There is a relative lack of research and methods for the purification and digestion of radiolarians in water bodies and sediments, which affects the application of radiolarians as key indicators in the study of marine environmental evolution, paleoclimate, and paleoceanography. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for purifying radiolarians in water or sediments, which effectively removes organic matter or authigenic silicoaluminate rocks and keeps their siliceous shell structure intact, and digests the purified radiolarians through a high-temperature reactor or high-concentration alkali to reduce sample loss.

[0005] The first aspect of the present invention provides a method for purifying radiolarians in water or sediments. The purification flow chart is as follows: Figure 1 As shown, the following steps are included:

[0006] (A1) Mix 5–15 mg of radiolarians collected from water with 3 mL of 25–30% hydrogen peroxide for 1–3 h. Then add 1.5–2 mL of 1 mol / L nitric acid solution and gently mix for 0.4–1 h.

[0007] Alternatively, 5–15 mg of radiolarians from sediment were mixed with 3 mL of 25–30% hydrogen peroxide for 1–3 h, ultrasonically shaken for 30–50 seconds, and then 3–5 mL of 1 mol / L nitric acid solution and 0.5–2 mL of 0.1 mol / L surfactant were added and gently mixed for 0.4–1 h.

[0008] (A2) Ultrasonic vibration for 30-50 seconds and place at room temperature for 8-10 hours;

[0009] (A3) The radiolarian solution is removed, the sample is thoroughly washed, centrifuged and dried to obtain a purified radiolarian sample.

[0010] In step (A1), high concentration of hydrogen peroxide can effectively remove radiolarian organic matter.

[0011] Furthermore, the surfactant is an alkyl methanesulfonic acid, which is used to separate mineral particles in radiolarian skeletons, etc. Other surfactants can also be used, but they should avoid contaminating the sample.

[0012] Furthermore, the ultrasound is 20-30KHz; using a lower frequency and multiple short-time ultrasonic oscillations (20-30KHz, <60 seconds) to treat radiolarians can reduce the risk of damaging the radiolarian skeleton and effectively remove the material attached to the radiolarian skeleton.

[0013] Furthermore, the sufficient cleaning is cleaning with deionized water for 3 to 5 times.

[0014] Furthermore, the drying is to freeze the radiolarians at -20°C and then perform low-temperature vacuum freeze-drying, or to dry them in an oven at a temperature below 60°C; low-temperature vacuum freeze-drying is preferred, as it does not destroy the crystalline water in the radiolarian skeleton.

[0015] The second aspect of the present invention provides a method for digesting the purified radiolaria. The digestion flow chart is as follows: Figure 2 As shown, the following steps are included:

[0016] (B1) 5-10 mg of purified radiolarians were reacted with 0.2-0.5 g of sodium hydroxide pellets in a high-temperature reactor at 120-180°C for 12-24 h, and then dissolved and diluted with 1-3 mL of deionized water;

[0017] Alternatively, mix 5-10 mg of radiolarians with 10-30 mL of 3-5 mol / L sodium hydroxide solution and place in a water bath at 85-95°C for 36-48 hours, then cool down.

[0018] (B2) Dilute acid is added to neutralize the sodium hydroxide to obtain a digested radiolarian solution for subsequent chemical analysis.

[0019] Furthermore, the dilute acid is dilute hydrochloric acid or dilute nitric acid.

[0020] Compared with the prior art, the beneficial effects of the present invention include at least:

[0021] 1. The purification method of the present invention does not involve a high-temperature pretreatment step, does not change the physical structure and chemical properties of the amorphous silicon of radiolarians, and can effectively remove organic matter and authigenic aluminosilicate rocks on the radiolarian skeleton.

[0022] 2. The digestion method of the present invention has a wide range of applications, high digestion efficiency, and fewer intermediate processes, thus avoiding sample loss. It can be used to digest fresh radiolarians in water bodies or radiolarians in sediments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Flow chart for radiolarian purification;

[0024] Figure 2 This is the flow chart of radiolarian digestion after purification;

[0025] Figure 3 This is a scanning electron microscope image of radiolaria in ocean water. Figure 3 A in the middle is before purification, Figure 3 B is after purification

[0026] Figure 4 This is a scanning electron microscope image of radiolaria in marine sediments. Figure 4 A in the middle is before purification, Figure 4 Middle B is after purification;

[0027] Figure 5 This is the elemental analysis diagram after radiolaria purification treatment. The C element is the signal of the carbon tape used to stick the radiolaria, and the Au element is the coating artificially added to improve the conductivity of the sample. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and beneficial effects of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. Examples of the embodiments are shown in the accompanying drawings. It should be understood that the specific embodiments described in the following embodiments of the present invention are only exemplary descriptions of the specific embodiments of the present invention, intended to be used for explaining the present invention, and do not constitute a limitation of the present invention.

[0029] The endpoints of ranges and any values disclosed herein are not limited to the exact range or value, and these ranges or values should be understood to include approximations to these ranges.

[0030] Example 1: Method for Purifying Radiolaria from Water and Sediments

[0031] The purification process of radiolaria in water and sediment is as follows: Figure 1 As shown, it involves the purification of radiolarians in water bodies and sediments: for radiolarians in water bodies, the main purpose is to remove organic matter; for radiolarians selected from sediments, because they have low organic matter content and more authigenic aluminosilicate rocks attached to the surface, the main purpose is to remove the authigenic aluminosilicate rocks.

[0032] (1) Purification of radiolarians from marine waters:

[0033] About 10 mg of radiolaria was mixed with 3 mL of high-concentration hydrogen peroxide (30%). After about 2 hours, 2 mL of 1 mol / L nitric acid solution was added and gently mixed. After 0.5 hours, ultrasonic vibration was applied for 30-50 seconds (20KHz). After standing at room temperature for about 8-10 hours, the hydrogen peroxide and nitric acid mixture was removed and 5 mL of deionized water was added to wash away the residual reagents. This washing process was repeated 3 times to ensure that the residual reagents were completely removed. After centrifugation and removal of the deionized water, the radiolaria was frozen at -20°C and then freeze-dried by low-temperature vacuum. Scanning electron micrographs of radiolaria before and after purification from marine waters are shown below. Figure 3 As shown, Figure 3 A in the middle is the radiolaria before purification. It can be seen that in addition to the siliceous skeleton, the radiolaria also contains some organic matter and other substances. Figure 3 Middle B is the purified radiolarian. You can see that a relatively complete siliceous skeleton remains after the purification process.

[0034] (2) Purification of radiolarians from marine sediments:

[0035] Approximately 10 mg of radiolaria was mixed with 3 mL of high-concentration hydrogen peroxide (30%). After 0.5 h, the mixture was ultrasonically shaken for 30-50 seconds (20 kHz). After about 2 h, 4 mL of 1 mol / L nitric acid solution was added and gently mixed. 1 mL of 0.1 mol / L alkyl methanesulfonic acid was then added. After 0.5 h, the mixture was ultrasonically shaken again for 30-50 seconds (20 kHz). After standing at room temperature for about 8-10 h, the hydrogen peroxide and nitric acid mixture was removed and 5 mL of deionized water was added to wash away any remaining reagents. This washing process was repeated three times to ensure complete removal of any remaining reagents. After centrifugation and removal of the deionized water, the radiolaria were frozen at -20°C and then freeze-dried by vacuum lyophilization.

[0036] Scanning electron micrographs of radiolarians in marine sediments before and after purification Figure 4 As shown, before purification ( Figure 4 A) Radiolarian skeletons have visible authigenic aluminosilicate rocks, and after purification ( Figure 4 B) is removed.

[0037] After purification, radiolarians were analyzed by scanning electron microscopy and energy dispersive analysis, and it was found that the main elements were Si and O, and no elements such as Al and Fe were found. Figure 5and Table 1), while the small amount of Cl and Ca found could be removed by washing with deionized water.

[0038] Table 1: Relative content of elements after radiolarian purification

[0039]

[0040] The C element in the table is the signal of the carbon tape used to stick radiolaria. The Au element content is not counted in the system. Tests 1, 2, and 3 correspond to Figure 4 The measured areas are 1, 2, and 3 (i.e., Spectre 1, 2, and 3).

[0041] Example 2: Digestion of purified radiolarians

[0042] The digestion method and process of purified radiolaria are as follows: Figure 2 As shown, this involves two methods: using a high-temperature reactor and hot alkaline solution digestion. In a laboratory with a high-temperature reactor, an appropriate amount (generally 5-10 mg) of radiolaria can be placed in a Teflon container with 0.5 g of sodium hydroxide pellets, tightly capped, and secured in the high-temperature reactor. The reactor is then placed in an oven set to 150°C for 24 hours, then closed. Once the sample temperature has cooled to room temperature, the reactor is opened and 1 mL of deionized water is added to dissolve the contents of the Teflon container. An appropriate amount of hydrochloric acid or dilute hydrochloric acid is added to neutralize the alkaline solution (sodium hydroxide solution) for subsequent chemical analysis. In the absence of a high-temperature reactor, 5-10 mg of radiolaria can be placed in a 50 mL centrifuge tube, mixed with 20 mL of a 4 mol / L sodium hydroxide solution (high concentration), and then placed in an 85-95°C water bath for 48 hours of shaking. After the reaction, the sample is cooled in the laboratory, neutralized with dilute hydrochloric acid or nitric acid, and used for subsequent chemical analysis.

[0043] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and do not constitute a limitation of the present invention. Within the technical concept of the present invention, the technical solutions of the present invention may be subjected to various simple modifications, including combining the various technical features in any other appropriate manner. These simple modifications and combinations should also be considered as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for purifying radiolarians in water or sediment, characterized in that: The steps include: (A1) Mix 5–15 mg of radiolarians collected from water with 3 mL of 25–30% hydrogen peroxide for 1–3 h. Then add 1.5–2 mL of 1 mol / L nitric acid solution and gently mix for 0.4–1 h. Alternatively, 5–15 mg of radiolarians from sediment were mixed with 3 mL of 25–30% hydrogen peroxide for 1–3 h, ultrasonically shaken for 30–50 seconds, and then 3–5 mL of 1 mol / L nitric acid solution and 0.5–2 mL of 0.1 mol / L surfactant were added and gently mixed for 0.4–1 h. (A2) Ultrasonic vibration for 30-50 seconds and place at room temperature for 8-10 hours; (A3) The radiolarian solution is removed, the sample is thoroughly washed, centrifuged and dried to obtain a purified radiolarian sample.

2. The purification method according to claim 1, wherein The surfactant is alkyl methanesulfonic acid.

3. The purification method according to claim 1, wherein The ultrasound is 20-30 KHz.

4. The purification method according to claim 1, wherein The sufficient cleaning is to use deionized water to clean for 3 to 5 times.

5. The purification method according to claim 1, wherein The drying step is to freeze the radiolarians at -20°C and then freeze-dry them in a vacuum oven, or to dry them in an oven at a temperature below 60°C.

6. A method for decomposing radiolarians, characterized in that: The steps include: (B1) 5-10 mg of purified radiolarians were reacted with 0.2-0.5 g of sodium hydroxide pellets in a high-temperature reactor at 120-180°C for 12-24 h, and then dissolved and diluted with 1-3 mL of deionized water; Alternatively, mix 5-10 mg of radiolarians with 10-30 mL of 3-5 mol / L sodium hydroxide solution and place in a water bath at 85-95°C for 36-48 hours, then cool down. (B2) adding dilute acid to neutralize the sodium hydroxide to obtain a digested radiolarian solution; The purified radiolaria is purified by the purification method according to any one of claims 1 to 5.

7. The digestion method according to claim 6, wherein The dilute acid is dilute hydrochloric acid or dilute nitric acid.

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